[skeb] add extractor for followed users (#5290)

needs 'Authorization' header from browser session
-o headers.Authorization="Bearer ey…"

docs/supportedsites.md

@@ -790,7 +790,7 @@ Consider all listed sites to potentially be NSFW.
 <tr>
     <td>Skeb</td>
     <td>https://skeb.jp/</td>
-    <td>Followed Users, Posts, Search Results, User Profiles</td>
+    <td>Followed Creators, Followed Users, Posts, Search Results, User Profiles</td>
     <td></td>
 </tr>
 <tr>